254 A. M. Mayer—Floating Magnets. 
from the pole of the superposed magnet. Thus we see how 
the same atoms endowed with forces of the same strength, may 
take different relative positions, and thus produce very different 
crystal-forms in the same matter. We may take 5a for an 
illustration of the atomic arrangement in the diamond, while 
may stand for graphite. But there is always a change of 
density accompanying the different forms in allotropy, and this 
fact is also illustrated by configurations 5a and 5d. In bodies 
formed of the same kind of elementary atoms, as in allotropy, 
it is evident that their relative —" ern ‘be directly as the 
number of atoms contained in the unit of volume. As our con- 
figurations illustrating allotropy ann the: same number of 
magnets, it follows that the relative densities of these configura- 
‘tions are inversely as their areas. Now the area of 5a (measured 
on the original prints) is 818 square iliion and the area of 
5b is 992 square millimeters, hence the density of 5a is to the 
density of 56 as 992 is to 818. Thus we see how the arrange- 
ment of magnets in 5a may stand for the — cE 
in the diamond while 5 may stand for that in gra 
Numerous instances exist in chemistry of the same sadeleiets 
combined in the same ortions, yet producing bodies erys- 
tallizing in different forms, and having different densities, color, 
transparency, hardness, etc. examples of this phenomenon 
of isomerism we may cite calcium carbonate, which crystallizes 
in two forms differing in density, viz: as cale spar of a specific 
gravity of , and as aragonite of a specific gravity of 2°93. 
ih ccs 6a may stand for the molecular structure of calc 
apar, while 6b may stand for that of pc Pete relative 
47. 
ann d ntl 4-25. These three isomers may be illustrated 
by 8, 8b and 8a, which have respectively the densities of 382, 
364 and 360. 
actions which, in the experiments, take place in a plane, may 
similarly take place among repelling and attracting points sit- 
nate in space of three dimensions. 
Other forms of the Kaperiments.—Instead of floating the —, 
nets they may be suspended by fine silk fibers. In this m ~— 
of experimenting the attractive action of the supe agnet 
is replaced by the action of gravity, which draws the mutually 
repellant needles toward the vertica 
